Data from Helios 1 are examined to find an experimental fit for the T(V) relationship at 1 AU. The data show a distinct change in the proton temperature-velocity slope at V~500 km s-1. For V>500 km s-1, T=(0.77¿0.021)V-(265¿12.5), while for V<500 km s-1, T1/2=(0.031¿0.002)V-(4.39¿0.08) or T1/3=(0.0106¿0.001)V -(0.278¿0.03). These results are compared to the results of Burlaga and Ogilvie (1973) and show excellent agreement in the V<500 km s-1 range. In addition, the secular variation of T(V) is examined, and it is found that the above functional forms still provide a good fit for a 2-year interval approaching solar minimum and a 2-year interval approaching solar maximum.